#include <ctype.h>
#include <stdbool.h>
#include <stdio.h>
#include <string.h>

#define MAXLINEWIDTH (79)

void usage(){
	fprintf(stderr,
		"Usage: bin2c [inputfile] [outputfile]\n"
		"\n"
		"Converts a binary file to a C string that denotes the same binary contents, but\n"
		"is parseable by a C compiler.\n"
		"Default values for the arguments are stdin and stdout; also '-' indicates the\n"
		"standard stream.\n");
}

// Returns serialised string length
// Keeps state on the previous few characters to aid compression and prevent
// trigraphs
int serialisechar(char *dst,unsigned char c){
	static bool lastwasoctal=false;
	static unsigned char prevc;

	switch(c){
		case '\a': lastwasoctal=false; prevc=c; dst[0]='\\'; dst[1]='a'; return 2;
		case '\b': lastwasoctal=false; prevc=c; dst[0]='\\'; dst[1]='b'; return 2;
		case '\f': lastwasoctal=false; prevc=c; dst[0]='\\'; dst[1]='f'; return 2;
		case '\n': lastwasoctal=false; prevc=c; dst[0]='\\'; dst[1]='n'; return 2;
		case '\r': lastwasoctal=false; prevc=c; dst[0]='\\'; dst[1]='r'; return 2;
		case '\t': lastwasoctal=false; prevc=c; dst[0]='\\'; dst[1]='t'; return 2;
		case '\v': lastwasoctal=false; prevc=c; dst[0]='\\'; dst[1]='v'; return 2;
		case '"':  lastwasoctal=false; prevc=c; dst[0]='\\'; dst[1]='"'; return 2;
		case '\\': lastwasoctal=false; prevc=c; dst[0]='\\'; dst[1]='\\'; return 2;
		default:
			if(c<32||c>=127){
				lastwasoctal=true;
				prevc=c;
				return sprintf(dst,"\\%o",(int)c);
			} else if(isdigit(c)&&lastwasoctal&&prevc<'\100'){
				prevc=c;
				return sprintf(dst,"\\%o",(int)c);
			} else if(c=='?'&&prevc=='?'){
				lastwasoctal=false;
				dst[0]='\\'; dst[1]='?';
				return 2;
			} else {
				lastwasoctal=false;
				dst[0]=c;
				prevc=c;
				return 1;
			}
	}
}

// Returns new xposition
int convertbuffer(FILE *output,const char *buffer,int length,int xposition){
	char cbuf[8];
	for(int i=0;i<length;i++){
		int clen=serialisechar(cbuf,buffer[i]);
		if(xposition+clen>MAXLINEWIDTH){
			fputc('"',output);
			fputc('\n',output);
			fputc('"',output);
			xposition=1;
		}
		fwrite(cbuf,1,clen,output);
		xposition+=clen;
	}
	return xposition;
}

void bin2c(FILE *input,FILE *output){
	fputc('"',output);

	char buffer[1024];
	int xposition=1;

	while(true){
		size_t nread=fread(buffer,1,sizeof(buffer),input);
		if(nread==0){
			break;
		}
		xposition=convertbuffer(output,buffer,nread,xposition);
		if(feof(input)||ferror(input)){
			break;
		}
	}

	fputc('"',output);
	fputc('\n',output);
}

int main(int argc,char **argv){
	if(argc==1){
		bin2c(stdin,stdout);
	} else if(argc==2){
		if(strcmp(argv[1],"-h")==0||strcmp(argv[1],"--help")==0){
			usage();
		} else if(strcmp(argv[1],"-")==0){
			bin2c(stdin,stdout);
		} else {
			FILE *f=fopen(argv[1],"rb");
			if(!f){
				fprintf(stderr,"Could not open file '%s'\n",argv[1]);
				return 1;
			}
			bin2c(f,stdout);
			fclose(f);
		}
	} else if(argc==3){
		FILE *fin,*fout;
		if(strcmp(argv[1],"-")==0){
			fin=stdin;
		} else {
			fin=fopen(argv[1],"rb");
			if(!fin){
				fprintf(stderr,"Could not open file '%s'\n",argv[1]);
				return 1;
			}
		}

		if(strcmp(argv[2],"-")==0){
			fout=stdout;
		} else {
			fout=fopen(argv[2],"wb");
			if(!fout){
				fprintf(stderr,"Could not open file '%s'\n",argv[2]);
				return 1;
			}
		}

		bin2c(fin,fout);

		fclose(fin);
		fclose(fout);
	} else {
		usage();
		return 1;
	}
}